MECHANISlVf OF LEAF-STALK3. JgJ 



for myself; but they would take up too much room, Sir, in 

 your Journal : I shall therefore give only a specimen of what 

 I mean by a gatherer; and a representation of the leaf- 

 stalk dissected. 



No person can have examined a tree with attention, with- The beautiful 

 out observing the beautiful arrangement of its leaves ; the ^"angement 

 exquisite manner in which they are prevented from obstruct- 

 ing- the light, or keeping the air from each other, and the 

 yario s curious contrivances (especially with large leaves) 

 manifested in raising or depressing them, so as to prevent 

 their throwmg too deep a shade on each other, and on 

 those that are beneath them. It is to the gatherers alone 

 they are indebted for this, to the power the two ends of 

 the peduhcle have of turning through the third of a circle, 

 that they are able to place themselves in this manner, and 

 arrange their leaves in such beautiful order, so conducive 

 to their benefit and future health. 



The peduncle may generally be divided into three parts, 

 and, if it has any mechanism to manage, which it is sel- 

 dom without, it is always found in two of these parts, that 

 which joins the peduncle to the stem, and that which unites 

 the leaf to the peduncle. PI. V, fig. 1, is a drawing of »:he Explanation of 

 peduncle of the liburnum or cytisus. AJB are the two ga- 

 therers; and C D are the same extremely magnified, and 

 dissected ; it is easy to see, that the spiral wire being much 

 contracted may draw these into various figures, according as 

 it is tight or loose within the gatherers, as it is at ee, and may 

 turn them three parts of a circle; and thus make the leaf 

 or leaf-stalk measure a very extensive circumference ; and 

 by this means accommodating its neighbour, and placing 

 itself in the most eligible situation, not only for its leaf, but 

 for the buds which are trusted to its care, and generally in 

 the axilla of its peduncle. The gatherers at both ends 

 appear, when much contracted, like a screw at the exte- 

 rior, and sometimes they are so bent as to be doubled, but 

 at another time you will hardly be able to see that they 

 do gather, so various is their figure. 1 shail now show a Description ©f 



specimen of a leaf-stalk, which comes nearer in gradation , '"^^'^^S® 

 . . . ... polymorpha. 



to the sensitive plant;, one of the medicagoes, differing little 



from the trifoliuras, and many of the diadelpbiau plants. 



Fig. 



